Centering coupling for electrical submersible pump splined shafts

ABSTRACT

An electrical submersible well pump assembly having a pump, a pump motor, and a seal section. The motor drives the pump via shafts rotatingly coupled with a coupling assembly. The coupling assembly maintains the shaft ends in coaxial alignment with an alignment device. The alignment device is profiled on opposite ends for mating engagement with the centering profiles on the shaft ends.

FIELD OF THE INVENTION

This invention relates in general to electrical submersible well pumps,and in particular to couplings between splined shafts of an electricalsubmersible pump.

BACKGROUND OF THE INVENTION

Electrical submersible pumps (ESP) are commonly used for hydrocarbonwell production, FIG. 1 provides an example of a submersible pumpingsystem 10 disposed within a wellbore 5. The wellbore 5 is lined withcasing 4 and extends into a subterranean formation 6. Perforations 9extend from within the wellbore 5 through the casing 4 into theformation 6. Hydrocarbon fluid flow, illustrated by the arrows A, exitsthe perforations 9 into the wellbore 5, where it can either be pumped bythe system 10 or migrate to a wellhead 12 disposed on top of thewellbore 5. The wellhead 12 regulates and distributes the hydrocarbonfluid for processing or refining through an associated production line7.

The pumping system 10 includes an electrical submersible pump (ESP) 14with production tubing 24 attached to its upper end. The ESP 14comprises a motor 16, an equalizer or seal 18, a separator 20, and apump 22. A fluid inlet 26 is formed in the housing in the region of theESP 14 proximate to the separator section 20. The fluid inlet 26provides a passage for the produced hydrocarbons within the wellbore 5to enter the ESP 14 and flow to the pump 22. Fluid pressurized by thepump 22 is conveyed through the production tubing 24 connecting the ESP14 discharge to the wellhead 12. The pump 22 and separator 20 arepowered by the motor 16 via a shaft (not shown) that extends from themotor 16. The shaft is typically coupled to respective shafts in each ofthe pump 22, separator 20, and seal 14.

Delivering the rotational torque generated by an ESP motor 16 typicallyinvolves coupling a motor shaft (i.e., a shaft connected to a motor orpower source) to one end of a driven shaft, wherein the other end of thedriven shaft is connected to and drives rotating machinery. Examples ofrotating machinery include a pump, a separator, and tandem pumps. Onetype of coupling comprises adding splines on the respective ends of theshafts being coupled and inserting an annular collar over the splinedends, where the annular collar includes corresponding splines on itsinner surface. The rotational force is well distributed over thesplines, thereby reducing some problems of stress concentrations thatmay occur with keys, pins, or set screws. Examples of a splinecross-section include an involute and a square tooth. Typically, splineshaving an involute cross-section are smaller than square tooth splinesthereby leaving more of the functional shaft diameter of a shaft tocarry a rotational torque load. Additionally, involute spline shapesforce the female spline to center its profile on the male spline, thuscoaxially aligning the shafts in the coupling with limited vibration.Square tooth splines are made without specialized cutters on an ordinarymill. However square teeth spline couplings do not align like involuteteeth unless the clearance is reduced or the male and female fittingsare forced together. However, reducing clearance or force fitting squareteeth splines prevents ready assembly or disassembly.

SUMMARY OF THE INVENTION

Disclosed herein is a submersible pumping system for pumping wellborefluid, comprising, a pump motor, a seal section, a motor shaft having anend rotatably affixed within an end of a shaft coupling, the motor shaftrotatable by the motor, a driven shaft having an end rotatably affixedwithin an end of the shaft coupling opposite to the motor shaft, therespective ends of the motor shaft and driven shaft being substantiallycoaxial within the shaft coupling, and an alignment element provided inthe shaft coupling, the element coaxially engaging the respectiveterminal ends of the motor shaft and driven shaft within the shaftcoupling. Optionally, the alignment element may be disposed on a shaftend. A first centering guide may be included on one side of thealignment element and a second centering guide on the alignment elementopposite side, the first centering guide being substantially coaxialwith the second centering guide. The first and second centering guidesmay be one of a protrusion on a side of the alignment element or arecess bored in the alignment element. A motor shaft tip alignmentmember may be included on the end of the motor shaft within the couplingand a driven shaft tip alignment member provided on the end of thedriven shaft within the coupling. The tip alignment members may be aprotrusion on the end of a shaft or a recess bored into the shaft.Square tooth splines may be formed on the motor shaft and driven shaftrespective ends. An axial bore can be formed through the coupling wheresquare tooth splines are formed on the bore inner diameter. In oneembodiment, the driven shaft drives rotating machinery, where themachinery may be a pump, a tandem pump, and a separator. A resilientmember may be included with the alignment element. The resilient membercan be used to align the shafts with an opposing force in the absence ofa shaft thrust load.

Also disclosed herein is a method of using an electrical submersiblepump (ESP) in a wellbore involving providing the ESP in the wellbore.The ESP may include a motor, a motor shaft rotatingly affixed to themotor; a rotating device, a driven shaft rotatingly affixed to therotating device, and a coupling rotatingly affixing ends of the motorshaft and driven shaft. The method may further include energizing themotor thereby rotating the motor shaft, the coupling, and the drivenshaft. Additionally, the present method includes substantially coaxiallyaligning the ends of the motor shaft and driven shaft during shaftrotation. The method optionally further comprises providing an alignmentelement in the coupling between the shaft ends, and coaxially mating theshaft ends with the alignment element. A resilient member may beincludable with the alignment element. The shaft ends can be profiledfor coaxial alignment. The shaft end profile might include a protrusionor a recess bored into the shaft end. The method can also includeprofiling a side of the alignment element to align with the shaft ends.Profiling can involve forming a protrusion on a side of the alignmentelement and forming a recess bored into a surface of the alignmentelement.

The present disclosure also includes an electrical submersible pump(ESP) comprising a pump motor, a motor shaft mechanically affixed to thepump motor, a seal portion, a pump, a pump shaft mechanically affixed tothe pump, a connector assembly rotatingly coupling respective terminalends of the motor shaft and the pump shaft, and an aligning pin in theconnector assembly axially engaged on one end with a terminal end of thepump shaft and axially engaged on another end with a terminal end of themotor shaft, wherein the pump shaft, motor shaft, and aligning pin axesare substantially aligned. A profile can be included on the aligning pinconfigured to engage the shaft ends, wherein the profile may be aprotrusion or a recess. A resilient member may be included with thealigning pin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a prior art submersible electrical pumpingsystem in a wellbore.

FIG. 2 a is an exploded view of a shaft coupling for use with the systemof FIG. 1.

FIG. 2 b is an assembled view of the shaft coupling of FIG. 2 a.

FIG. 3 a is an exploded view of an alternative shaft coupling for usewith the system of FIG. 1.

FIG. 3 b is an assembled view of the shaft coupling of FIG. 3 a.

FIG. 4 a is an exploded view of an alternative shaft coupling for usewith the system of FIG. 1.

FIG. 4 b is an assembled view of the shaft coupling of FIG. 4 a.

FIG. 5 is a side partial cut-away view of an alternative shaft couplingfor use with the system of FIG. 1.

FIG. 6 is a side partial cut-away view of an alternative shaft couplingfor use with the system of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter withreference to the accompanying drawings in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theillustrated embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Like numbers refer to like elements throughout. For the convenience inreferring to the accompanying figures, directional terms are used forreference and illustration only. For example, the directional terms suchas “upper”, “lower”, “above”, “below”, and the like are being used toillustrate a relational location.

It is to be understood that the invention is not limited to the exactdetails of construction, operation, exact materials, or embodimentsshown and described, as modifications and equivalents will be apparentto one skilled in the art. In the drawings and specification, there havebeen disclosed illustrative embodiments of the invention and, althoughspecific terms are employed, they are used in a generic and descriptivesense only and not for the purpose of limitation. Accordingly, theinvention is therefore to be limited only by the scope of the appendedclaims.

The present disclosure includes a square tooth spline coupling withvibration control. The coupling disclosed herein provides sufficientclearance between the respective male and female splines providing readyassembly and disassembly. With reference now to FIG. 2 a, an explodedside partial cutaway view of one embodiment of a coupling assembly andrespective shafts is provided. As noted above, during operation of apumping assembly, a motor shaft is powered by a pump motor, eitherdirectly or through a shaft coupling. The coupling assembly provides amanner of connecting the motor shaft to a driven shaft that drivesrotating machinery. The coupling connection also transfers rotationalenergy between the motor and driven shaft, thus providing power for therotating machinery.

The coupling assembly 30 of FIG. 2 a comprises an annular collar 48 witha bore 50 formed lengthwise therein. Female splines 52 extend axiallyalong the bore 50 inner surface. The bore 50 diameter transitions at apoint to form a shoulder 56 that is substantially perpendicular to thecollar 48 axis A_(X). An alignment element 54 is on the shoulder 56. Inthe embodiment shown, the alignment element 54 has a disc-likemidsection and disposed in the collar 48 with its midsection axis (notshown) largely aligned with or parallel to the collar axis A_(X). Thealignment element 54 outer diameter exceeds the shoulder 56 innerdiameter and its lower side butts on the shoulder 56. The outer diameterfits closely in the bore 50. An insert or sleeve 60 is coaxiallyreceived within the collar 48 in the portion of the bore 50 having anincreased diameter. The insert 60 extends from the upper surface of thealignment member 54 terminating at the upper end of the collar 48. Theinsert 60 is optionally threaded on its outer diameter to mate withcorresponding threads provided on the collar 48 inner diameter. Femalesplines 52 are formed along the insert 60 inner diameter. Positioningthe insert 60 against the alignment element 54 toward the shoulder 56,retains the alignment element 54 within the collar 48.

Centering guides (62, 63) are shown extending from the upper and lowersurface of the alignment element 54. In this embodiment, the centeringguides (62, 63) comprise conically shaped protusions. Above and belowthe coupling assembly 30 are an upper shaft 32 and lower shaft 40. Theupper shaft 32 lower end 36 is provided with male splines 34 configuredfor coupling engagement with the female splines 52 of the couplingassembly 30. Similarly, the lower shaft 40 upper end 44 includes malesplines 42 configured for coupling engagement with the female splines52. The shafts (32, 40) are profiled on their terminal ends forcentering engagement with the centering guides (62, 63) of the alignmentelement 54. In the embodiment shown, the profiling on the shaftscomprises recesses or bores (38, 46) extending from the terminal matingtips of the shafts and substantially aligned with the respective axes(A_(SH), A_(SL)) of the upper or counterbore lower shafts (32, 40). Eachrecess (38, 46) has a conical entry way with a taper matching thecentering guides (62, 63). The recess and protrusion provide examples ofguide profiles formed on the shaft ends and alignment element forengaging the shaft ends to the alignment element. During pumpingoperations, impellers in the pump create an axial thrust force in thepump shaft forcing the shafts (32, 40) together and engaging thecentering guides (62, 63) with the recesses (38, 46).

Referring now to FIG. 2 b, an example of an assembled shaft coupling isshown in side cross-sectional view. The male splines 34 on the lower end36 of the upper shaft 32 engage the female splines 52 and the uppershaft 32 bore 38 mates with the centering guide 62 that extends from thealignment element 54. Similarly, the male splines 42 on the upper end 44of the lower shaft 40 are engaged with the female splines 52 of thecollar 48 and the bore 46 on the upper terminal end of the shaft 40mates with the centering guide 63 that extends from the opposite side ofthe alignment element 54. The upper shaft 32 and lower shaft 40 arealigned along a common axis within the collar 48 thus preventing shaftvibration when one of the shafts energizes the other.

FIG. 3 a shows an alternative embodiment of a shaft coupling 30 a forcoupling an upper shaft 36 a to a lower shaft 44 a. In this embodiment,the alignment element 54 a has a largely disc-like cross-sectional areaand is seated on the shoulder 56. The insert 60 retains the element 54 awithin the collar 48. The centering guides (62 a, 63 a) comprise aconical profile bored into the body of the alignment element 54 a.Similarly, the terminal tips of the upper shaft 36 a and lower shaft 44a include conically profiled protrusions (39, 47) formed to engaged thebores of the centering guides (62 a, 63 a). FIG. 3 b illustrates theassembled shaft coupling 30 a and engagement of the protrusions (39, 47)with the centering guides (62 a, 63 a). This configuration also controls shaft vibration during transmission of torque through the coupling 30a. The profiles on the alignment elements and the terminal tips of theshafts are not limited to the figures described herein, but can includeother shapes such as conical, concave, convex, spherical or other curvedsurfaces. Additionally, cylindrical profiles with may be employed andmay include rounded tips on the cylinder end.

Yet another embodiment of a shaft coupling 30 b is provided in sidecross-sectional view in FIG. 4 a. In this embodiment, the centeringguides 62 b and centering guide 63 b comprise a raised profile on therespective upper and lower sides of the alignment element 54 b. Thealignment element 54 b comprises an upper housing 64, a lower housing66, and a resilient member housed within the upper and lower housings(64, 66). One example of a resilient member is a spring 68. In thisembodiment, the upper and lower housing (64, 66) both comprise agenerally cup-like structure having a closed base that is largelyperpendicular to the axis of the collar 48 a. The housings have sidesextending from the base towards an open end, the sides lie generallyconcentric with the axis A_(X) of the collar 48 a. The upper housing 64inner diameter is greater than the lower housing 66 outer diameterallowing insertion of the lower housing 66 into the upper housing 64 intelescoping relation. The spring 68 provides a resilient force forurging the upper and lower housing (64, 66) apart.

As shown in FIG. 4 b, in some embodiments, a vertical force may move theshaft (32, 40) toward one another and pushes on one of the upper orlower housing (64, 66), thereby compressing the spring 68 there between.One of the advantages of this embodiment is an axial force from one ofthe shafts (32, 40) is fully absorbed by the spring 68 and nottransferred to the other or any other adjacent shaft within a pumpingsystem. Moreover, the resilient nature of the spring 68 can force thehousings (64, 66) apart upon absence of the vertical force whilecontinuing axial alignment of the shafts (32, 40) during operation ofthe pumping system. Because rotational shafts in an ESP seal portiontypically are not subjected to axial thrust, the resilient feature maybe useful for these couplings. As shown, the housings (64, 66) haveprotrusions profiled on their respective outer surfaces formed to matchrecesses (38, 46) on the shafts (32, 40). However, the housings (64, 66)could be fashioned to include recesses and the shafts (32, 40) havingcorresponding protrusions.

Another embodiment illustrating ESP shaft coupling is provided in a sidepartial cut-away view in FIG. 5. Here an upper shaft 36 b and lowershaft 44 b are aligned with a retaining pin 70 that extends from a bore38 b in the lower terminal end of the upper shaft 36 b into acorresponding bore 46 b in the upper terminal end of the lower shaft 44b. The retaining pin 70 may include an annular shoulder 71 radiallydisposed around the body of the pin 70 approximately at its mid-section.To accommodate the retaining pin 70, the bores (38 b, 46 b) are formeddeeper into the shafts (36 b, 44 b) than the bores (38, 46) illustratedin FIGS. 2 a and 2 b.

A coupling assembly is presented in side partial cross sectional view inFIG. 6 that combines concepts described above. An upper shaft 36 with abore 38 is disposed within a collar 48 b into coaxial alignment with acorresponding lower shaft 44 b. A protrusion 47 a extends from the lowershaft 44 b upper terminal end into the bore 38 and is retained thereinfor coaxial alignment of the shafts (36, 44 b). The protrusion 47 a ofFIG. 6 is similar to the protrusion 47 of FIGS. 3 a and 3 b, but hasincreased dimensions, including an increased length, to ensure matingcooperation with the bore 38. The collar 48 b inner diameter is smallerat its upper end to match the upper shaft 36 outer diameter. The collar48 b can be machined or forged as a uni-body configuration, or reducedwith an insert (not shown) similar to the collar 48 of FIGS. 2 a-3 b.

The present invention described herein, therefore, is well adapted tocarry out the objects and attain the ends and advantages mentioned, aswell as others inherent therein. While a presently preferred embodimentof the invention has been given for purposes of disclosure, numerouschanges exist in the details of procedures for accomplishing the desiredresults. These and other similar modifications will readily suggestthemselves to those skilled in the art, and are intended to beencompassed within the spirit of the present invention disclosed hereinand the scope of the appended claims. While the invention has been shownin only one of its forms, it should be apparent to those skilled in theart that it is not so limited but is susceptible to various changeswithout departing from the scope of the invention.

1. A submersible pumping system for pumping wellbore fluid, comprising:a pump motor; a splined shaft coupling; a motor shaft having a splinedend rotatably affixed within one end of the shaft coupling, the motorshaft being rotatable by the motor; a driven shaft having a splined endrotatably affixed within an opposite end of the shaft coupling oppositeto the motor shaft, the respective ends of the motor shaft and drivenshaft being substantially coaxial within the shaft coupling; a guideprofile on the splined end of each shaft; and an alignment elementmounted in the shaft coupling, the element coaxially engaging the guideprofiles on the ends of the motor shaft and driven shaft within theshaft coupling.
 2. The pumping system of claim 1, further comprising afirst centering guide on one side of the alignment element and a secondcentering guide on the alignment element opposite side, the firstcentering guide being substantially coaxial with the second centeringguide each centering guide engaging a corresponding guide profile. 3.The pumping system of claim 2 wherein the first and second centeringguides selectively comprise a protrusion or a recess.
 4. The pumpingsystem of claim 1 wherein the guide profiles on the shafts are conicaland located on each shaft axis.
 5. The pumping system of claim 1,wherein the guide profiles comprise a protrusion or a recess.
 6. Thepumping system of claim 1, wherein the coupling has internal squaretooth splines.
 7. The pumping system of claim 1, wherein the alignmentmember comprises a disk mounted in the coupling, the disk beingperpendicular to the coupling axis.
 8. The pumping system of claim 1further comprising a shoulder formed in the coupling, and a threadedsleeve secured within the coupling, wherein the alignment elementcomprises a disk secured between the shoulder and the sleeve.
 9. Thepumping system of claim 1, wherein the alignment element comprises upperand lower housings that telescope relative to one another, and aresilient member.
 10. An electrical submersible pump (ESP) comprising: apump motor; a motor shaft mechanically affixed to the pump motor; adriven shaft; a splined coupling rotatingly coupling respective splinedends of the motor shaft and the driven shaft; a tapered centeringprofile on the splined ends of each shaft coaxial with each shaft axis;and an alignment device mounted in the coupling the alignment devicehaving a tapered guide profile on one side that mates with the centeringprofile on the motor shaft and a tapered guide profile on an oppositeside that mates with the centering profile on the driven shaft.
 11. TheESP of claim 10 wherein the tapered centering profiles and the taperedguide profiles are conical.
 12. The ESP of claim 18, wherein thealignment device comprises an upper housing and a lower housing, eachhousing having one of the guide profiles, and a spring located betweenthe upper housing and the lower housing urging the upper housing and thelower housing apart.
 13. A method of connecting a live shaft of an ESPpump motor to a driven shaft, the shafts having splined ends, the methodcomprising: providing a guide profile on each splined shaft end;mounting an alignment element within a splined coupling; and insertingthe splined shaft ends into the coupling and engaging profiles on thealignment element.
 14. The method of claim 13, wherein the profilecomprises a protrusion and the alignment element comprises a recessconfigured to receive the protrusion.
 15. The method of claim 13,wherein the alignment element comprises a protrusion and the profilecomprises a recess configured to receive the protrusion.
 16. The methodof claim 13, wherein the shaft ends are maintained coaxial within thecoupling by engaging the profiles with the alignment element.
 17. Themethod of claim 13, wherein the alignment element comprises a diskmember having profiles on its upper and lower surface, the methodfurther comprising mounting the alignment element perpendicularly in thesplined coupling.